Nuclear Theory·nucl-th

Tuesday·July 28, 2026

20 papers—14 primary·6 cross-listed

01
[Submitted on 24 Jul 2026]
What we talk about when we talk about nuclear structure
S. Ragnar Stroberg
I provide and introductory overview of the field of nuclear structure, with a focus on physical concepts. I describe some basic nuclear structure observables, followed by a qualitative description of nuclear forces. I then outline some nuclear structure models which are most widely used to interpret the experimental data in terms of interacting protons and neutrons.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2607.22887 [pdf]
1 citation
02
[Submitted on 25 Jul 2026]
Future directions in nuclear $β$ decay at FRIB and beyond
Garrett B. King🇺🇸 · Ayala Glick-Magid🇮🇱 · Grigor Sargsyan🇺🇸 · Mark A. Caprio🇺🇸 · Kyle G. Leach🇨🇦 · John A. Behr🇨🇦 · Francesca Bonaiti🇺🇸 · Maxime Brodeur🇺🇸 · Graham Chambers-Wall🇺🇸 · Heather L. Crawford🇺🇸 · Maria Dawid🇺🇸 · Wouter Dekens🇺🇸 and 29 other authors
Motivated by the opportunities presented for studies relevant to nuclear structure, astrophysics, and fundamental symmetries with nuclear $β$ decay, the Facility for Rare Isotope Beams (FRIB) Theory Alliance topical program ``Future Directions in Nuclear $β$ Decays at FRIB'' was held in September of 2025. This white paper summarizes the main points of discussion over the two-week program, and it aims to provide a snapshot of the current status of the field while also highlighting important questions and opportunities for future work. We provide an overview of the experimental tools and techniques that enable modern $β$ decay studies, discuss the current state of nuclear many-body approaches used to study $β$ decays, and highlight the important science questions that can be addressed by weak decays.
Comments:
90 pages, 10 figures; Whitepaper of FRIB TA Topical Program "Future directions in nuclear beta decay at FRIB"
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2607.22983 [pdf]
1 citation
03
[Submitted on 25 Jul 2026]
Determination of asymptotic normalization coefficients for the $^{7}$ Li $\to α +^{3}$ He channel
L.D. Blokhintsev · B.F. Irgaziev · D.A. Savin
Asymptotic normalization coefficients (ANCs) $C_{3/2}$ and $C_{1/2}$ for the channels $^{7}$ Li $(3/ 2^{-}; 0$ MeV) $\to α +^{3}$ H and $^{7}$ Li $(1/ 2^{-}; 0.478$ MeV) $\to α +^{3}$ H, respectively, were determined by analyzing elastic $α^{3}$ H- scattering data using three different methods. All three methods yield similar results. The ANC values averaged over the three methods are $C_{3/2} = 2.08 \pm 0.10$ fm $^{- 1/2}$ and $C_{1/2} = 2.00 \pm 0.10$ fm $^{- 1/2}$ . Comparison of the found ANCs with the previously obtained ANCs for $^{7}$ Be confirms the relationship linking the ANC values for mirror nuclei.
Comments:
7 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.23158 [pdf]
0 citations
04
[Submitted on 25 Jul 2026]
Proton Collectivity in Au+Au Collisions at $s_{NN} = 2.4 - 4.5$ ~GeV from a Unified Purely Hadronic EOS without QCD Phase Transition
Gao-Feng Wei · Shuang-Jie Liu · Yu-Liang Zhao · Qi-Jun Zhi · Zhigang Xiao
The nuclear equation of state (EOS) is generally considered to soften in the density range of $2 - 5$ times the saturation density $ρ_{0}$ . Using a purely hadronic transport model, we calculate the proton directed, sideward, and elliptic flows and their excitation functions in heavy-ion collisions (HICs) at $s_{NN} = 2.4 - 4.5$ ~GeV and compare with the HADES, E895, and STAR data. We find that a momentum-dependent mean field with a unified incompressibility $K_{0} = 230$ ~MeV quantitatively reproduces the experimental proton flows up to 4.3 GeV, at which the maximum density reaches approximately $5 ρ_{0}$ . At 4.5 GeV, however, the pure hadronic model fails to reproduce the proton directed and elliptic flow data, providing circumstantial evidence for the onset of partonic degrees of freedom in HICs. Our results provide a hadronic baseline to characterize the high-density nuclear matter and to map the region of hadron-quark phase transition.
Comments:
5 Pages, 5 Figures and 37 references
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2607.23195 [pdf]
0 citations
05
[Submitted on 25 Jul 2026]
$^{15}$ C inelastic $1/ 2^{+} \to 5/ 2^{+}$ excitation: A single-particle versus a collective process
C. Beckman🇺🇸 · M. Catacora-Rios🇺🇸 · C. Hebborn🇫🇷 · F. M. Nunes🇺🇸
Background: The excitation of one-neutron halo nucleus $^{15}$ C from the $1/ 2^{+}$ ground state to the $5/ 2^{+}$ first excited state was measured at Argonne National Laboratory by impinging $^{15}$ C on a deuterated target at $7.1 A$ MeV. This data was then analyzed in the Distorted Wave Born Approximation using a rigid rotor model for the excitation. Purpose: Being a one-neutron halo, we expect a single-particle excitation to better represent the excitation of $^{15}$ C rather than a collective process. We expect the breakup of $^{15}$ C to influence the reaction mechanisms because of the low one-neutron separation threshold, which is close in energy to $^{15}$ C's first excited state. The goal of this work is to explore various the reaction mechanisms to reinterpret the data of Ref.[1] for the inelastic excitation of $^{15}$ C. Method: We solve the scattering problem assuming a three-body model $^{14}$ C $+ n + d$ . We use the Continuum Discretized Coupled Channel method (CDCC) and compare the results with those obtained assuming 1-step DWBA with quadrupole deformation, as done in the original experimental analysis. We also use Bayesian uncertainty quantification to estimate the uncertainties in our predictions coming from the $n$ - $d$ interaction. Results: We analyze both the elastic and inelastic angular distributions for $^{15}$ C(d,d') $^{15} C^{*}$ at $7.1 A$ MeV. Our results show that $^{15}$ C breakup effects are important. Conclusions: While CDCC predicts the elastic angular distribution correctly, it is not able to fully describe the experimental inelastic angular distribution. We discuss additional effects that may be responsible for the remaining discrepancy.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2607.23291 [pdf]
PRC(2026)·0 citations
06
[Submitted on 26 Jul 2026]
Sensitivity of $^{107, 109}$ Ag( $α$ ,xn) cross sections to statistical-model inputs
Arunabha Saha
The $α$ -induced reactions on silver isotopes leading to the production of the medically relevant radionuclides $^{108 m, 109 g, 110 m, 110 g, 111 g}$ In have been systematically analyzed using the TALYS~2.0 code. A total of 192 combinations of nuclear reaction model parameters, comprising level-density models (LDM), $α$ -optical model potentials ( $α$ OMP), and pre-equilibrium (PE) models, were evaluated through $χ^{2}$ minimization against the available experimental data. The results reveal pronounced channel-dependent sensitivities of the statistical-model ingredients. The $^{107}$ Ag( $α$ ,3n) $^{108 m}$ In and $^{109}$ Ag( $α$ ,3n) $^{110 g}$ In reactions are primarily governed by the LDM. For the $^{107}$ Ag( $α$ ,2n) $^{109 g}$ In reaction, the sensitivities to the LDM and PE mechanism are comparable, indicating that both contribute nearly equally to reproducing the experimental data. In contrast, the $^{107}$ Ag( $α$ ,n) $^{110 m}$ In and $^{109}$ Ag( $α$ ,2n) $^{111 g}$ In reactions are dominated by the PE mechanism, while the $α$ OMP plays a secondary role and the LDM has only a minor influence. These findings demonstrate that the relative importance of the statistical-model ingredients varies significantly among the investigated reaction channels. Differences between the present TALYS calculations and the TENDL-2023 evaluation are attributed to the absence of parameter optimization in the present study. Overall, the analysis shows that no single parameter combination provides the best description of all investigated reactions. The observed channel-dependent sensitivities provide useful guidance for selecting and evaluating TALYS model ingredients for the studied reaction channels and motivate future work incorporating additional experimental data and model-uncertainty quantification.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.23477 [pdf]
0 citations
07
[Submitted on 27 Jul 2026]
Systematic Parameter Optimization of Quantum Molecular Dynamics Models for Hadron Therapy Using Multi-Ion Fragmentation Data
Akihiro Haga · Yoshi-hide Sato · Daiyu Fujiwara · Dousatsu Sakata · Yuki Tominaga · David Bolst · Edward C. Simpson · Susanna Guatelli
Quantum molecular dynamics (QMD) models are widely used to simulate nuclear fragmentation in hadron therapy, but their predictive accuracy depends strongly on parameters that are often selected empirically. We developed an optimized QMD framework by systematically calibrating three parameters for a relativistic mean-field model with the NS2 parameter set and Skyrme models with the SLy4 and SkM* parameter sets: the wave-packet width L, maximum evolution time Tm, and impact-parameter envelope factor benv. The wave-packet width was determined from experimental charge radii, whereas Tm and benv were parameterized as functions of incident kinetic energy and reaction-system mass and optimized using proton- and heavy-ion-induced fragmentation data over 30-400 MeV/u. Performance was compared with the original LiQMD, Binary Cascade, and Liege Intranuclear Cascade models. The optimized Tm depended strongly on incident energy but only weakly on system mass, indicating that the transition from the dynamical QMD stage to statistical de-excitation is governed mainly by collision energy. In contrast, benv showed model-dependent behavior: NS2 favored larger peripheral-collision contributions for lighter systems at low energies, whereas the Skyrme models showed relatively weak energy and mass dependence. The optimized parameterizations improved agreement with experimental fragment production cross sections, angular distributions, and energy distributions. The optimized Skyrme models achieved the best overall performance and outperformed the cascade models for most datasets. This framework provides a physically consistent description of nuclear fragmentation across multiple observables and may improve calculations of secondary-particle transport, dose deposition, and linear energy transfer in hadron therapy.
Comments:
42 pages, 7 figures, 9 tables, submitted to PMB
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.24034 [pdf]
0 citations
08
[Submitted on 27 Jul 2026]
Study the Longitudinal Entropy Deposition using d+Au Collision
Zhu Meng · Weiyao Ke · Long-Gang Pang
Relativistic hydrodynamics successfully describes bulk observables in symmetric heavy-ion collisions, but struggles to reproduce charged-particle rapidity distributions in asymmetric systems such as d+Au collisions. To address this challenge, we introduce two key improvements to the initial-state modeling: sampling deuteron configurations from an ab initio wavefunction, and developing a new longitudinal entropy deposition model that incorporates a transverse entropy deposition coefficient $β$ and a rapidity loss term scaling with the number of binary collisions $n_{BC}$ . Using the (3+1)-dimensional viscous hydrodynamic model CLVisc coupled with the SMASH afterburner, we simulate d+Au collisions at $s_{NN} = 200$ GeV and successfully reproduce the experimental charged-particle pseudorapidity distributions across five centrality classes with $β = 0.35$ , as well as the transverse momentum spectra and anisotropic flow $v_{n}$ . The entropy deposition coefficient $β$ and the $n_{BC}$ -dependent rapidity loss are found to play crucial roles in achieving this agreement. Furthermore, this longitudinal entropy deposition framework demonstrates excellent universality, as validated in p+Au, $^{3}$ He+Au, and Au+Au collisions. Our entropy deposition mechanism could be widely applied to recent light-nucleus collisions such as O+O, Ne+Ne, and asymmetric systems like Pb+Ne at LHC energies, thereby better constraining the nuclear structure of light nuclei through an improved longitudinal description.
Comments:
20 pages, 16 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2607.24153 [pdf]
0 citations
09
[Submitted on 27 Jul 2026]
Microscopic Spin-Parity Distributions of Fission Fragments
Guillaume Scamps · Petar Marević · Antonio Bjelčić · Nicolas Schunck
Recent microscopic studies have investigated various features of the spin distributions of fission fragments, but their parity distributions remain largely unexplored. In this Letter, we provide a complete characterization of the spin--parity content of fission fragments within a time-dependent Hartree-Fock-Bogoliubov framework, performing for the first time simultaneous projections on angular momentum, particle number, and parity. Calculations are carried out for the thermal neutron-induced fission of $^{239}$ Pu using both the Gogny and Skyrme energy density functionals. We find that dynamical pair breaking during fission populates a significant fraction of unnatural-parity states and generates components with non-zero spin projections $K$ . The parity content is found to depend on the number parity of the fragments, with odd-mass nuclei exhibiting pronounced parity staggering and odd-odd nuclei favoring negative parity. These results show that the parity distribution of fragments can depart significantly from the equiprobable partition commonly assumed in statistical de-excitation models, with potential implications for the modeling of fragment decay.
Comments:
7 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2607.24156 [pdf]
0 citations
10
[Submitted on 27 Jul 2026]
3-body cluster gas structures in the excited $0^{+}$ states of $N = 6$ nuclei
Kosei Nakagawa · Yoshiko Kanada-En'yo
We investigate the cluster structure of $α +^{2} n +^{2} n$ in $^{8} He (0_{2}^{+})$ and compare it with those of $2 α +^{2} n$ in $^{10} Be (0_{2}^{+})$ and $3 α$ in $^{12} C (0_{2}^{+})$ to understand the emergence mechanism of the 3-body cluster gas states. We apply an extended cluster model combined with cluster breaking components in a microscopic framework using effective nuclear forces based on nucleon degrees of freedom including the antisymmetrization between nucleons. In detailed analysis of the 3-body cluster structures of excited $0^{+}$ states, it is shown that $^{8} He (0_{2}^{+})$ exhibits 3-body cluster gas feature of $α +^{2} n +^{2} n$ similar to $^{12} C$ but contains significant mixing of a 2-body-like $(α +^{2} n) +^{2} n$ component. We discuss cluster structures of $^{8} He (0_{2}^{+})$ and $^{12} C (0_{2}^{+})$ from the point of view of inter-cluster energies of $^{2} n -^{2} n$ and $α -^{2} n$ in comparison with the $α - α$ energies and find that the origin for the 2-body-like $(α +^{2} n) +^{2} n$ mixing is the unbalance of the $α -^{2} n$ and $^{2} n -^{2} n$ energies, in which Pauli effects play an essential role through the kinetic energy loss and internal potential energy loss of clusters. We clarify the emergence mechanism of the 3-body cluster gas state in excited $0^{+}$ states of $^{8} He$ and $^{12} C$ systems. The balance of inter-cluster interactions is essential for the appearance of 3-body cluster gas states. Microscopic effects, i.e., the Pauli effects of nucleons between clusters play a crucial role in cluster structures of excited $0^{+}$ states.
Comments:
18 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.24211 [pdf]
0 citations
11
[Submitted on 27 Jul 2026]
Interaction fingerprints in temperature-fluctuation cumulants from the QCD crossover to nuclear liquid-gas criticality
Debasish Mallick
Temperature fluctuations of the matter produced in relativistic heavy-ion collisions are related to event-by-event fluctuations of the mean transverse momentum and, through the specific heat, to the QCD equation of state. We calculate the temperature-fluctuation cumulants $c_{2}$ , $c_{3}$ , and $c_{4}$ in the ideal hadron resonance gas (HRG), in an excluded-volume HRG consistent with lattice QCD constraints on baryon repulsion, and in a van der Waals HRG that reproduces the nuclear ground state. At zero baryon density all three models agree with lattice QCD thermodynamics up to the chiral crossover and separate above it. Along the chemical freeze-out curve the models remain close for $s_{N N} ≳ 20$ GeV and separate strongly at lower energies, where baryonic interactions dominate the thermal response. In the van der Waals model the variance $c_{2}$ develops a minimum along the Widom line of the nuclear liquid-gas transition and $c_{3}$ changes sign across it. Temperature cumulants thus connect mean-transverse-momentum fluctuations to thermodynamic structures in two regions of the QCD phase diagram.
Comments:
9 pages, 7 figures; acknowledgments updated
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2607.24616 [pdf]
0 citations
12
[Submitted on 27 Jul 2026]
Emergence of the halo in $^{11}$ Li from full nuclear many-body dynamics
Yilong Yang · Pengwei Zhao
The two-neutron halo nucleus $^{11}$ Li is a paradigmatic quantum many-body system whose large spatial extent and weak binding have long challenged a microscopic description from first principles. Using a neural-network variational Monte Carlo approach, we present an \textit{ab initio} demonstration that the halo structure of $^{11}$ Li emerges directly from the underlying nuclear interactions and full many-body dynamics. The calculation employs an essential nuclear Hamiltonian constrained solely by few-body observables and reproduces the binding and separation energies of Li isotopes, as well as the isotopic trend of their matter radii. We identify a correlation between the halo size in $^{11}$ Li and the splitting of $P$ -wave neutron-alpha scattering phase shifts, establishing the crucial role of neutron-alpha spin-orbit interactions in halo formation. Dineutron correlations are found to arise naturally from the many-body wave function without assuming a preformed core-plus-valence-neutron structure. These results provide a microscopic understanding of halo formation in $^{11}$ Li and establish a link between few-body scattering observables and emergent many-body structure.
Comments:
5 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.24636 [pdf]
0 citations
13
[Submitted on 27 Jul 2026]
Light clusters in warm magnetized stellar matter: equation of state and thermodynamic response
Luigi Scurto · Stefano Burrello · Maria Colonna
Finite-temperature equations of state (EOSs) with a controlled treatment of composition-dependent effects are becoming increasingly important for modeling proto-neutron stars and binary neutron star merger remnants, where warm matter may coexist with strong magnetic fields. At sub-saturation densities, light nuclear clusters may also emerge with sizeable abundances. For beta-equilibrated matter, with or without neutrino trapping, an interplay between magnetic fields and light-cluster formation naturally arises in determining the matter composition: charge neutrality and weak equilibrium transmit the effects of Landau quantization to the baryonic sector, modifying the equilibrium charge content; at the same time, light-cluster formation also favors the increase of the proton fraction by binding protons into nuclear clusters. In this work, we investigate this interplay within a generalized relativistic mean-field framework, in which light clusters up to alpha particles are included as explicit degrees of freedom and their in-medium dissolution is described through phenomenological binding-energy shifts. We show that the formation and subsequent dissolution of light clusters, combined with magnetic-field effects, leave characteristic signatures in the matter pressure, the isothermal squared speed of sound, and the heat capacity, leading to significant modifications of the thermodynamic stiffness of the EOS and of the heat-storage properties of warm stellar matter. Furthermore, we investigate the impact of the isovector terms of the EOS, namely its symmetry energy, on these features. These results provide microscopic insights relevant to modeling the hydrodynamic and thermal evolution of proto-neutron stars and neutron star merger remnants, while establishing a baseline for the development of more comprehensive finite-temperature EOSs for compact-star applications.
Comments:
15 pages, 11 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2607.24660 [pdf]
0 citations
14
[Submitted on 27 Jul 2026]
Two-neutrino double-weak decays of $^{126}$ Xe and $^{134}$ Xe from different many-body methods
C. Brase · L. Jokiniemi · E. Kauppinen · B. Romeo · J. Kotila · J. Menéndez · A. Schwenk
We calculate the nuclear matrix elements and corresponding half-lives for the two-neutrino double-electron capture of $^{126}$ Xe and the two-neutrino double-beta decay of $^{134}$ Xe. We use different many-body methods: the proton-neutron quasiparticle random-phase approximation, the nuclear shell model, the microscopic interacting boson model, and an effective field theory for heavy nuclei. For both nuclei, all our half-life predictions are generally consistent with each other when including theoretical uncertainties for each method. Interestingly, for all calculations the lower range of the predicted $^{134}$ Xe half-life is shorter than $T_{1/2}^{2 ν} \approx 2 \times 1 0^{24}$ \,y, which may be within the reach of next-generation experiments. For $^{126}$ Xe, our results typically predict one order of magnitude longer half-lives than those for $^{134}$ Xe.
Comments:
15 pages, 9 figures, appendix included
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2607.24684 [pdf]
0 citations
15
[Submitted on 26 Jul 2026] (cross-list from hep-ph)
Effects of flavor-mixings on charged kaon and pion parton distribution functions
Fabio L. Braghin🇧🇷 · Parada T. P. Hutauruk🇯🇵
We investigate the charged kaon and pion parton distribution functions (PDFs) in the U(3) Nambu--Jona-Lasinio (NJL) model, considering a novel flavor-mixing interaction arising from vacuum polarization that differs from the instanton-induced 't~Hooft interaction. In this work, the proper-time regularization scheme is employed, and, effectively, it might take quark confinement into account. The gap equations, the meson masses, and the meson--quark coupling constants are calculated in the presence of flavor mixing interactions. The valence-quark distributions of the charged kaon and pion are calculated and compared with existing experimental data and JAM analysis results at scales $μ^{2} =$ 4 and 27 GeV $^{2}$ . The strength of mixing effects on the PDFs is found to be proportional to the quark effective masses and their differences. We further find that the dominant flavor mixing effects in the pion valence up-quark distribution at scales $μ^{2} =$ 27 and 4 GeV $^{2}$ are around $x ≃ 0.3$ and $x ≃ 0.8$ , while for the kaon, the effects are shown at around $x ≃ 0.2$ and $x ≃ 0.7$ . We also find similar strength of mixing effects on the PDFs at both scales $μ^{2} = 4$ and 27 GeV $^{2}$ ; however, it certainly improves the pion and kaon PDFs.
Comments:
13 pages, 9 figures, and 2 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2607.23497 [pdf]
1 citation
16
[Submitted on 27 Jul 2026] (cross-list from hep-th)
Near-Light-Cone Nonhydrodynamic Structure from Boosted Hydrodynamics
Navid Abbasi🇨🇳 · Jewel Kumar Ghosh🇧🇩 · Dirk H. Rischke🇩🇪
Hydrodynamics provides a universal description of many-body systems at long wavelengths. Its long-lived collective excitations, known as hydrodynamic modes, admit long-wavelength expansions whose convergence is encoded in the analytic structure of retarded correlators of conserved quantities in thermal equilibrium. We show that a boost can change which nonhydrodynamic singularity limits such an expansion. In the large-boost limit, the relevant singularity originates in the large-momentum, near-light-cone region of the rest-frame spectrum. After factoring out the Lorentz-factor growth, the rescaled convergence scale is controlled by the microscopic spectral structure of the theory. We explicitly demonstrate this in two examples: relaxation-time kinetic theory and holography.
Comments:
25 pages, 8 figures, 1 table. v2: Updated the caption of Fig. 3 and made a few minor corrections
Subjects:
High Energy Physics — Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2607.24576 [pdf]
0 citations
17
[Submitted on 27 Jul 2026] (cross-list from hep-lat)
First constraints on the nonperturbative gluon Collins-Soper kernel
Artur Avkhadiev🇺🇸 · Yang Fu🇺🇸 · Phiala E. Shanahan🇺🇸 · Michael L. Wagman🇺🇸 · Yong Zhao🇺🇸
The gluon Collins-Soper kernel, which encodes the rapidity evolution of transverse-momentum-dependent gluon distributions, is constrained for the first time in the nonperturbative regime, for transverse momentum scales $q_{T} \in [300 MeV, 1.3 GeV]$ . The constraints are determined in lattice QCD at a close-to-physical pion mass $M_{π} = 172 (3) MeV$ , a single lattice spacing $a = 0.15 fm$ , and next-to-next-to-leading logarithmic matching in Large-Momentum Effective Theory. These results represent the first step toward a controlled determination of the gluon Collins-Soper kernel in QCD, with eventual phenomenological import and relevance to present and future experiments sensitive to the gluon structure of hadronic matter.
Comments:
24 pages, 16 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2607.24587 [pdf]
0 citations
18
[Submitted on 27 Jul 2026] (cross-list from hep-lat)
Analytic decomposition of two-body electroweak processes with left-hand cuts
André Baião-Raposo🇩🇪 · Raúl A. Briceño🇺🇸 · Nicolas Lang🇪🇸 · Felipe G. Ortega-Gama🇺🇸 · Bianca Pol🇺🇸
We derive an on-shell representation for electroweak $2 + J \to 2$ transition amplitudes involving two hadrons in both the initial and final state for systems where there are left-hand singularities generated by light-particle exchange, e.g. one-pion exchange. The derivation treats the insertion of the electroweak current perturbatively, keeping only the leading-order contribution in the external field, while the hadronic interactions are treated to all orders, including one-particle exchange effects. We find that, in such processes, the amplitude can have logarithmic singularities, as well as one-particle pole singularities, due to these exchanges. We isolate those contributions, as well as previously identified triangle singularities. The result is expressed in terms of the purely hadronic amplitude, exchange-current kernels, triangle functions, and a class of short-distance transition functions that are real and smooth below unaccounted-for thresholds. While we consider only transitions with spinless particles, this work is an important step toward constraining form factors of systems involving nucleons or vector mesons in the heavy quark sector, where the one-pion-exchange singularity is quite close to threshold.
Comments:
35 pages, 10 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2607.24648 [pdf]
0 citations
19
[Submitted on 27 Jul 2026] (cross-list from hep-ph)
Electromagnetic structure of charged and neutral strange vector mesons
Parada T. P. Hutauruk🇯🇵
We investigate the electromagnetic form factors (EMFFs) of the charged $K^{*+} (892)$ ( $u s ˉ$ ) and neutral $K^{0} (896)$ ( $d s ˉ$ ) strange vector mesons within the covariant Nambu--Jona-Lasinio (NJL) model, employing the Schwinger proper-time regularization scheme to regularize ultraviolet divergences while incorporating the QCD aspect of quark confinement. To this end, we evaluate the charge (electric) $G_{C} (Q^{2})$ , magnetic $G_{M} (Q^{2})$ , and quadrupole $G_{Q} (Q^{2})$ form factors, as well as the charge radii, of the charged $K^{+} (892)$ and neutral $K^{0} (896)$ strange vector mesons. We find the charge radii to be $⟨ r^{2} ⟩_{K^{+}} = 0.45 fm^{2}$ and $⟨ r^{2} ⟩_{K^{0}} = - 0.04 fm^{2}$ , respectively, while the corresponding magnetic moments are $μ_{K^{+}} = 2.67, μ_{N}$ and $μ_{K^{* 0}} = 0.032, μ_{N}$ . These results are consistent with other theoretical calculations and lattice QCD simulations.
Comments:
10 pages, 8 figures, 1 table
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2607.24661 [pdf]
0 citations
20
[Submitted on 27 Jul 2026] (cross-list from hep-ph)
Symbolic Extraction of Non-Perturbative Transverse-Momentum-Dependent Distributions from Drell-Yan Data
Cole Granger🇺🇸 · Alessandro Bacchetta🇮🇹 · Valerio Bertone🇫🇷 · Chiara Bissolotti🇺🇸 · Matteo Cerutti🇫🇷 · Marco Radici🇮🇹 · Simone Rodini🇮🇹 · Lorenzo Rossi🇮🇹 · Cristiano Fanelli🇺🇸
We present an analytical parametrization of the non-perturbative transverse-momentum-dependent (TMD) parton distribution function of unpolarized quarks, extracted from Drell-Yan data using a combination of neural-network fitting and symbolic regression. A factorized neural network is trained directly against experimental cross-section data from fixed-target, Tevatron, RHIC, and LHC experiments at next-to-next-to-next-to-leading logarithmic accuracy, and symbolic regression is subsequently applied to each network component to discover compact analytical expressions. The final formula is selected from a Pareto front in the space of expression complexity and experimental $χ^{2}$ , yielding a closed-form non-perturbative function with 9 free numerical constants that achieves $χ^{2} / ndf = 1.040$ over 482 data points. A non-trivial $x$ - $b_{T}$ cross term is retained even under a sparsity prior that biases it toward zero, indicating a mild but genuine correlation between the longitudinal momentum fraction and the transverse momentum. This work demonstrates that symbolic regression is a viable tool for bridging flexible machine-learning fits and interpretable analytical TMD parametrizations, and opens a systematic path toward data-driven discovery of specific features of non-perturbative QCD.
Comments:
11 pages, 3 figures, 2 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th); Data Analysis, Statistics and Probability (physics.data-an)
arXiv:
2607.24710 [pdf]
0 citations

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